Door latching mechanism



[Ap i 22,1969 JEAN-CLAUDE RENELAFFORGUE 3,440,403

' DOOR LATCHING MECHANISM Filed Aug. 14, 1967 FIG. 4

INVENTOR.

14 FIG.

J EAN CLAUDE R. LAFFORGUE ATTORNEY United States Patent Int. Cl. F21d 11 /00; A21b 1/22 US. Cl. 219-413 7 Claims ABSTRACT OF THE DISCLOSURE A door latch mechanism as for use with a kitchen appliance such as a self-cleaning baking oven. The mechanism includes a support means disposed in a door frame forming a door opening. A latch means is mounted on the support means for movement between door latched and door unlatched positions. A bimetallic strip has one end attached to the support means and the opposite end secured to the latch means. An electric heating element is arranged adjacent the bimetallic strip so that when it is energized the strip will move the latch means into the door latched position. An electric interlock switch means is operatively associated with the latch means so as to be actuated when the latch means is in its door latched position.

The present invention relates to a latching mechanism for locking a door and particularly for locking a door of a high temperature domestic cooking oven of the type having an automatic heat cleaning cycle such as is described in the patent of Bohdan Hurko, Patent No. 3,121,-

158 which is assigned to the General Electric Company, the assignee of the present invention.

Such an oven would have the normal cooking functions of baking and broiling within a temperature range between 150 F. and 550 F. as well as a heat cleaning operation where the temperature is raised to a maximum somewhere between 750 F. and 950 F. for removing the food soil and grease spatter that accumulates on the walls of the oven liner during cooking. In such a high temperature oven, it is of primary importance to latch the door before the cleaning cycle is set in motion and to hold it latched so that the door cannot be opened during the heat cleaning cycle. The oven control circuits are so designed that the heat cleaning cycle cannot be initiated until the door latch mechanism is in its closed position.

The principal object of the present invention is to provide a latch mechanism that automatically locks the oven door when the oven control circuitry has been set for a heat cleaning cycle and cooperates with the control circuitry to insure that the oven door is first closed before the temperature within the oven cavity may be made to rise above normal cooking temperatures and to insure that the oven door may not be unlocked while the temperature remains in the high temperature range.

The present invention, in accordance with one form thereof, embodies a novel latch mechanism for the door of a domestic oven which includes a support means disposed adjacent the access opening and a latch means mounted on the support means for movement between door latched and door unlatched positions. A bimetallic strip has one end attached to the support means and the other end secured to the latch means. An electric heating means is arranged in close vicinity to the bimetallic strip so that when energized the strip will move the latch means into the latched position. Finally an electric switch means is operatively associated with the latch means so as to be actuated by the latch means.

The invention Will be better understood from the following description taken in conjunction with the accompanying drawings and its scope will be pointed out in the appending claims.

FIG. 1 is a perspective view of an electric range with parts broken away to show the arrangement of the latch means.

FIG. 2 is a fragmentary plan view on an enlarged scale of the electric range showing the housing containing and supporting the latch means whereby the top of the housing has been partially removed to show the latch means in its open position disengaged from the oven door.

FIG. 3 is a plan view similar to FIG. 2 with the latch means in its fully closed position.

FIG. 4 is a side view of a bimetallic strip actuating the latch means.

FIG. 5 is a fragmentary plan view on an enlarged scale of a modification of the latch means shown in FIGS. 2 and 3.

In FIG. 1 there is illustrated a free-standing electric range 10 having a top cooking surface 11 with a plurality of surface heating elements 12, an oven cavity 13, a frontopening, drop-door 14 and a backsplasher 15 arranged along the back edge of the cooking surface 11. The backsplasher 15 contains a control panel 16 which governs the energization of the various heating elements, including a lower bake unit 17 which is arranged in the oven cavity 13 along the bottom thereof and an upper broil unit (not visible) arranged under the top of the cavity. As mentioned previously, this invention of a novel latch means has been found of primary importance when used with a heat cleaning oven of the type disclosed in the aforementioned Patent No. 3,121,158 of Bohdan Hurko. In such a heat cleaning oven there is a third heating element or mullion heater (not shown) that is located near the front opening of the oven cavity 13 in order to compensate for the loss of heat through and around the door opening. This mullion heater is the same type of heating element as the bake and broil units, namely, a sheathed wire resistance heater.

The oven cavity 13 is formed by a liner 18 of box-like configuration with an open front that is adapted to be closed by the oven door 14. Outside the oven cavity 13 and on top of its liner 18, there is mounted a housing 19 containing the novel latch means. In action the latch means will project through a slot 20 in the ouside wall of range 10 and enter into a corresponding slot 21 provided in door 14 thereby securing the door in its closed position.

As more clearly shown in FIGS. 2 and 3, the housing 19 is mounted by suitable means on top of liner 18 outside of oven cavity 13 and close to its access opening. Practically, housing 19 will abut front wall 22 of range 10 for a purpose that will be explained later. A latch means comprising an elongated straight section 23 having one end curved to form a hook 24 is hingedly secured within housing 19 by means of a pivot 25 for movement in a hori zontal plane. A bimetallic strip of a generally U-shaped configuration including two legs 26 and 27 connected by a bight portion 28 is attached with leg 27 to housing 19 and hingedly secured with leg 26 to the elongated straight body 23 by means of a swivel or universal joint 29. It is advantageous to prestress the bimetallic strip so that it acts as a spring to bias the latch means into the unlatched position which movement is limited by an end stop 30. Beneath the bimetallic strip is located an electric heating element 31 of the sheathed wire type in the form of a loop which may be an extension of mullion heater 32 arranged around the oven cavity 13 as previously mentioned. Finally, an electric switch 33 is mounted to housing 19 so as to be operated by the straight end 23 of the latch means. Lead wires 34 connect switch 33 with the control circuitry of electric range 10.

In operation, the latch means will perform automatically as follows:

When the control circuitry of electric range 10 has been set on the control panel 16 for an oven heat cleaning cycle, all heating elements of the oven inclding the mullion heating element 32 are energized. The looped extension 31 of the mullion heater starts to heat up the bimetallic strip and when a certain temperature T is reached, the bimetallic strip will move the latch means from the unlatched position shown in FIG. 2 into the latched position of FIG. 3. Thereby the hook-shaped end 24 of the latch means will project out of the slot 20, enter into slot 21 and so lock oven door 14 in the closed position. At the same time, the opposite end of the latch means operates switch 33 which will change the characteristic of the control circuitry in such a way that the oven temperature may now climb, to the height necessary for a heat cleaning performance.

The certain temperature T at which the bimetallic strip will move the latch means from the unlatched position to the latched position, is so selected that it falls within the range of the normal cooking temperatures in the oven, for instance, anywhere between 300 F. and 500 F. Also the control circuit is so designed that the temperature in the oven even if all three heating elements are energized, cannot exceed 550 F. unless switch 33 has been actuated. Thus, it is obvious that a malfunction of the latch means will not actuate switch 33 and thereby present the temperature in the oven to rise over 550 F.

The bimetallic strip may be designed to effect the motion of the latch means from one position to the other position gradually. However, the particular configuration of the bimetallic strip and its position relative to the latch means and the housing as illustrated in FIGS. 2, 3 and 4 provides for a rapid movement of the latch means. As FIG. 4 shows, leg 26 and bight portion 28 are dilferent in length also the angles on and B formed by legs 26 and 27 with bight portion 28 are not the same. This will prestress the bimetallic strip so that it will bias the latch means to the unlatched position if heating element 31 is not energized. On the other hand, if element 31 is energized the energy built up in bight portion 28 will prevent the energy built up in leg 26 from moving the latch means into the latched position until the predetermined temperature T is reached. At this temperature, there is then enough energy built up in leg 26 to overcome the opposing energy built up in bight portion 28 and to move the latch means very rapidly into the latched position. After the cleaning cycle in completed, the heating elements are de-energized and the temperature in the oven decreases. Approaching in the vicinity of temperature T, the opposite will take place and the spring biasing eifect of the bimetallic strip will move the latch means into the unlatched position whereupon the oven door may be opened.

It is obvious, that the novel latch mechanism may be modified in many ways without departing from the scope of this invention. Two of such modifications are included in the latch mechanism illustrated in FIG. wherein like numerals. To provide a true snap action like operation of the latch means, the bimetallic strip has been formed into a V-shaped configuration 35. One end of this strip 35 is attached to the housing 19 and its free end to one end of a tension spring 36 while the other end of spring 36 is connected to the latch means. This arrangement is, of course, a toggle mechanism which will provide a snap action like motion of the latch means between latched and unlatched positions. Also, instead of using an extension of mullion heater 32 for heating the bimetallic strip, a separate heating element 36 may be arranged beneath the bimetallic strip. This separate heating element is connected to the control circuitry of the range so that it will be energized when the range is set for a cleaning cycle.

While there have been shown and described some preferred embodiments of the present invention, it is to be understood that the invention is not limited thereto and it is intended to cover by the appended claims all such modifications within the true spirit and scope of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A latch mechanism for locking the door of an electric oven comprising: a support means disposed adjacent the open front of said oven to be closed by said door, a latch means pivotally mounted on said support for movement between door latched and door unlatched positions, a bimetallic strip having one end attached to said support and the other end hingedly secured to said latch means, a heating means arranged adjacent said bimetallic strip so that When energized said strip will move said latch means into the latched position thereof, and an electric switch operatively associated with said latch means so as to be actuated by the movement of said latch means.

2. An electric oven comprising: a cabinet having front, rear, side, top and bottom walls, an oven cavity in said cabinet fromed by an oven liner having a front opening closable by an access door, electric heating elements arranged in said cavity along the bottom and top thereof and around said front opening, a housing mounted on top of said oven liner adjacent said front opening, a hook hingedly mounted in said housing for movement between door latched and door unlatched positions, a bimetallic strip having one end attached to said housing and the other end hingedly secured to said hook, an electric heating element arranged within said housing adjacent said bimetallic strip so that when energized said strip will move said hook into a latched position, and an electric switch operatively associated with said hook so as to be actuated by the movement of said hook.

3. An electric oven comprising: a cabinet having front, rear, side, top and bottom walls, an oven cavity in said cabinet formed by an oven liner having a front opening closable by an access door, electric heating elements arranged in said cavity along the bottom and top thereof and around said front opening, a housing mounted on top of said oven liner adjacent said front opening, a hook hingedly mounted in said housing and adapted to project from said housing through a slot in the front wall of said cabinet into a corresponding slot provided in said access door, a bimetallic strip having one end attached to said housing and the other end hingedly secured to said hook, a portion of the heating element arranged around the front opening of said oven cavity extending into said housing so at to heat said bimetallic strips, and an electric switch operatively associated with said hook so as to be actuated by the movement of said hook.

4. An electric oven as defined in claim 3 wherein said hook comprises an elongated straight body having one end curved to form the hook and is hingedly secured to said housing between the curved end and the other straight end.

5. An electric oven a defined in claim 4 wherein the straight end of said hook engages said electric switch when being moved into the latched position.

6. An electric oven described in claim 3 wherein said bimetallic strip is of a generally U-shaped configuration including two leg portions connected by a bight portion.

7. An electric oven as defined in claim 3 wherein said bimetallic strip is of a V-shaped configuration having one References Cited UNITED STATES PATENTS 6/1965 Getman 219413 5/1967 Bowling 219412 6 3,313,918 4/1967 Barber 219412 3,350,542 10/ 196 7 Getman 2194-12 3,390,909 7/1968 Nagel 219413 X BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, Assistant Examiner.

US. Cl. X.R. 219412 

